This invention relates to a method of producing surfactants from lignin. More particularly, the invention discloses a process of sulfonating a lignin phenol and reacting the lignin phenol sulfonate with a reaction product of alkylphenol and formaldehyde. These compounds may be used in surfactant flooding to recover hydrocarbons from underground formations.
Surface active compounds or surfactants have become extremely important chemicals in our society. Numberless types of surfactants are used for a myriad of applications. To work effectively, most surfactants require water soluble and oil soluble characteristics. It is these mixed characteristics which enable surfactants to lower the surface tension between two disparate liquids.
One problem with many surfactants is their high cost of manufacture. Surfactants which are relatively cheap have an inherent advantage in the marketplace.
A minor use of surfactants has been in surfactant flooding systems for enhanced oil recovery. But because of the relatively high cost of surfactants, surfactant flooding systems for oil recovery have generally not been economical.
Surfactant flooding to recover oil has been actively investigated due to the relatively poor ability of waterfloods to displace remaining oil from a reservoir's pore structure. Because of the reservoir structure and surface tensions involved, the floodwater may form channels or fingers, bypassing the oil in the formation.
Investigations of ways to increase oil recovery by improving the displacement ability of waterfloods have produced useful surfactants which reduce the interfacial tension between oil and water in the reservoir. With lower interfacial tensions, oil that is trapped in the pore structure can be dispersed into the water as smaller and more easily deformable droplets. Many types of surfactants have been investigated and the choice of which surfactant to employ in a waterflood operation is dependent upon reservoir characteristics as well as the cost and availability of the surfactants.
Lignin is a by-product that the pulping industry produces in prodigious amounts. As a result, a large research effort has been undertaken over the last 40 years in attempts to find uses for the large volume of lignin by-product.
Lignin is comprised of polymeric chains having molecular weights over 10,000 with multiple different units. One substantial monomeric unit contained in the lignin polymeric chains is propane phenol.
U.S. Pat. Nos. 4,739,041 and 4,790,382 describe a method of producing water soluble surfactants from lignin which comprises subjecting lignin to two reactions, alkylation and oxidation. U.S. Pat. Nos. 4,739,040 and 4,787,454 disclose a method of surfactant flooding with lignin surfactants produced by reducing lignin in the presence of a carbon monoxide or hydrogen reducing agent at high temperature and pressure to produce low molecular weight lignin phenols, and subjecting the lignin phenols to one or a combination of several reactions such as alkoxylation, alkylation, sulfonation, sulfation, alkoxysulfation, and sulfomethylation.
Another water soluble lignin surfactant variation is disclosed in U.S. Pat. No. 4,781,251 wherein an alkylphenol lignin surfactant is employed in a surfactant flooding system. The alkylphenol lignin surfactant is produced by reacting an alkylphenol having about 6 to about 15 carbon atoms in the alkyl chain with formaldehyde in basic solution at elevated temperature to form a first reaction product. The first reaction product is then reacted with a kraft lignin at elevated temperature to form an alkylphenol lignin reaction product. Finally, the alkylphenol lignin reaction product is made more water soluble by a reaction selected from the group consisting of sulfonation, sulfation, alkoxysulfonation, alkylsulfation and alkoxylation to produce the alkylphenol lignin surfactant.
A copending application Serial No. 632,836, filed Dec. 24, 1990, discloses the preparation of an oil soluble lignin surfactant by reacting benzyl alcohol with lignin phenol and sulfonating the reaction product. A second copending application Ser. No. 464,480, filed Jan. 12, 1990, teaches a method of making an oil soluble lignin surfactant by alkoxylating lignin phenol and subjecting the alkoxylated lignin phenol to a second reaction of sulfonation, sulfation or alkoxysulfation.